EP1960131B1 - Method and device for producing a metal strip by continuous casting and rolling - Google Patents

Abstract

The invention relates to a method for producing a metal strip (1) by continuous casting and rolling. According to said method, a thin slab (3) is initially cast into a casting machine (2), which is subsequently rolled in at least one rolling train (4, 5) using primary heat from the casting cycle. According to the invention, in order to improve the functionality of the continuous casting and rolling installation, the cast thin slab (3) is passed between the casting machine (2) and the at least one rolling train (4, 5) and at least one holding oven (6) as well as at least one induction oven (7). The holding oven (6) and the induction oven (7) are activated or deactivated according to a selected mode of operation, that is, a first mode of operation for the continuous production of the metal strip (1) and a second mode of operation for the discontinuous production of the metal strip (1). The invention further relates to a device for producing a metal strip by continuous casting and rolling.

Description

The invention relates to a method for producing a metal strip by casting rolls, in which first a thin slab is cast in a casting machine, which is then rolled in at least one rolling train using the primary heat of the casting process. Furthermore, the invention relates to an apparatus for producing a metal strip by casting rolls. document EP-A 0610028 discloses a generic method and a generic device. Plants of this type are known as thin-slab thin-strip caster under the name CSP plants.

The endless rolling out of the casting heat has long been known, but it has not yet prevailed in the market. The rigid connection of continuous casting plant and rolling mill and the temperature control through the entire system have proven to be difficult to control.

From the EP 0 286 862 A1 and from the EP 0 771 596 B1 is the continuous rolling out of the casting heat known. Here, the casting and rolling processes are directly coupled. A separation of the endless belt with a pair of scissors is done just before the reel.

Similar processes for the continuous production of strip steel in the coupling of casting and rolling plant reveal the EP 0 415 987 B2 and the EP 0 889 762. B1 , To overcome the temperature problems at the relatively low transport speed inductive heaters are provided there before and within the rolling train.

An alternative technology for this is the rolling of single slabs or single bands. In the discontinuous rolling of belts, the casting and rolling are decoupled. The casting speed is usually very low and the rolling speed is independent of a high level in such a way that the temperature for the last transformation is above the minimum temperature. Such systems, which are also referred to as CSP systems are, for example, in the EP 0 266 564 B1 described where a high deformation in the thin slab plant is performed.

A similar thin slab plant also shows the EP 0 666 122 A1 where discontinuous ribbons are rolled between the first finishing stands using inductive heating.

The advantages of batch rolling are that the casting and rolling speeds can be adjusted independently. In Dünnbandwalzung can be z. B. flexibly set higher rolling speeds, even if the casting machine operates at low speed or the speed is being changed there.

Both methods - ie on the one hand the continuous casting rolls and on the other hand the discontinuous casting rolls - are difficult to combine due to the circumstances explained above.

The invention is therefore based on the object to remedy this situation and to provide a combined Gießwalzverfahren and associated devices with which or with both a continuous and a discontinuous operation is possible. The advantages of both processes should now be combined in a new plant concept.

The solution of this issue by the invention is procedurally characterized in that the cast thin slab between the casting machine and the at least one rolling train passes both at least one holding furnace and at least one induction furnace, the holding furnace and the induction furnace activated or deactivated depending on a selected mode, namely a first mode of continuous production of the metal strip and a second mode of discontinuous production of the metal strip or controlled or regulated. The order of the two furnaces, ie the holding furnace and the induction furnace, is arbitrary.

Preferably, the rolled metal strip can also be heated in the belt conveying direction behind a first rolling train in at least one further induction furnace, wherein the at least one further induction furnace is activated or deactivated or controlled or regulated as a function of the selected operating mode.

The choice of operating mode can be made depending on the final thickness of the metal strip to be generated or depending on the casting speed of the metal strip. It has also proved useful if it is provided that the choice of operating mode is made depending on the product of thickness and speed of the metal strip or the thin slab to be produced.

The operating mode can also be selected depending on the material to be processed. This can also be related to the respective permissible outlet temperature of the strip from the rolling mill.

For example, the continuous mode may be selected if the product of casting thickness and casting speed is greater than 70 mm × 6.5 m / min = 455,000 mm ² / min. Of course, depending on the material, this value can also be in a different range, whereby a value between 300,000 mm ² / min and 600,000 mm ² / min can be used as the criterion for the "switching point" from one mode to the other ,

An alternative criterion may be that the said mode is selected for end thicknesses of the metal strip of less than 2 mm.

Preferably, in the selected mode of operation of the discontinuous production of the metal strip, the thin slab is held batchwise in the holding furnace at a desired temperature before it is conveyed into the rolling train.

In the selected mode of continuous production of the metal strip, the thin slab in the holding furnace can be brought to a desired temperature and then heated to the desired rolling temperature by means of the induction furnace immediately before the rolling process in the rolling mill. It can be particularly preferably provided that the heat input into the thin slab takes place through the induction furnace as a function of the casting speed.

Depending on the casting speed, the continuous mode or the discontinuous rolling can be adjusted, so that the necessary final rolling temperature can be achieved in each operating case.

In order to achieve an optimal use of energy in the production of the metal strip, a development provides that the release of heat from the heated metal strip or from the thin slab to the environment is hindered by thermal insulation means. These do not have to be used constantly. It can therefore be provided that at least some of the heat-insulating means are moved into the area of the metal strip or moved out of this area depending on the desired operating mode of the cast-rolling plant.

An advantageous development provides that the metal strip in the rolling train in a front in the belt conveying direction range of the rolling line and then in a subsequent in the belt conveying direction Area is heated. Of course, this does not preclude the provision of further descaling devices.

The descaling of the metal strip or the thin slab by means of a descaling device and the heating of the metal strip or the thin slab by means of an induction furnace is preferably carried out between two rolling stands. The heating in the belt conveying direction can follow descaling or vice versa.

The apparatus for producing a metal strip by casting rolls, with a casting machine, in which a thin slab is first cast, and at least one rolling mill downstream of the casting machine, in which the thin slab is rolled using the primary heat of the casting process, according to the invention is characterized in that between the casting machine and the at least one rolling train at least one holding furnace and at least one induction furnace is arranged.

The appropriate control of both furnaces, ie the holding furnace and the induction furnace, allows - as will be seen in more detail - both an efficient continuous and an efficient discontinuous operation of the plant. For this purpose, control means are preferably provided with which depending on the selected mode, namely a first mode of continuous production of the metal strip and a second mode of discontinuous production of the metal strip, the holding furnace and / or the induction furnace is activated or deactivated or controlled or regulated.

In the conveying direction of the thin slab or the metal strip may first be arranged a holding furnace and then an induction furnace. Furthermore, an advance road and a finishing train may be provided, wherein a further induction furnace is arranged between the roughing train and the finishing train. Furthermore, at least one further induction furnace can be arranged between two rolling mills of the roughing train and / or the finishing train.

Behind the first induction furnace in the conveying direction of the thin slab or of the metal strip and in front of the finishing train, a band shears can advantageously be arranged. In addition to this, a thin-slab scissors can be arranged in a manner known per se in the conveying direction behind the casting machine and in front of the holding furnace. In the conveying direction behind the finishing train a band shear can be arranged.

A further embodiment provides that heat-insulating means for preventing the release of heat from the heated metal strip or from the heated thin slab to the environment are present, which are arranged at least temporarily in the region of the metal strip. In this case, preferably moving means are provided with which at least a part of the heat-insulating medium can be moved into the area of the metal strip or moved out of this area.

In most cases, however, the largest part of the thermal insulation will be arranged stationary.

Furthermore, provision can be made for at least one descaling device to be present, which is arranged in a front region of the rolling train in the belt conveying direction.

A particularly preferred embodiment of the invention provides that in the conveying direction of the thin slab or the metal strip in this order, a holding furnace, an induction furnace and a compensation furnace are arranged in front of the rolling train.

By using more efficient inductive heaters, which today build relatively space-saving and by a suitable plant constellation, which allow a continuous operation but also optionally a discontinuous rolling, the proposed procedure is favored.

• Es ergibt sich eine kurze Baulänge der Anlage und damit geringe Investitionskosten.

The advantages of the continuous technology, ie the continuous operation of the proposed system, in connection with the CSP technology are as follows:

• This results in a short length of the system and thus low investment costs.

It is possible to save energy as a result of consistent direct deployment.

Furthermore, a lower deformation resistance results due to the lower rolling speed.

The possibility is created difficult to roll products and z. B. very thin (ultra thin) bands (strip thickness of about 0.8 mm) to produce in high production volumes.

Special materials (high-strength materials) can be processed.

A combination of wide and thin ribbons can be processed.

Bandendenverwalzungen and thus roller damage can be avoided or reduced.

The disturbance rate of the system can be reduced and high speeds can be avoided.

In the drawings, embodiments of the invention are shown.

Fig. 1

schematisch eine Gießwalzanlage gemäß einer ersten Ausführungsform der Erfindung,

Fig. 2

in der Darstellung nach Fig. 1 eine Gießwalzanlage in einer alternativen Ausführungsform der Erfindung,

Fig. 3

in der Darstellung nach Fig. 1 eine Gießwalzanlage in einer weiteren alternativen Ausführungsform der Erfindung,

Fig. 4

schematisch den Bereich zwischen der Gießmaschine und der Walzstraße mit einer Schere und Mitteln zur Wärmedämmung,

Fig. 5

schematisch den Ausschnitt aus der Fertigstraße mit zwei Walzgerüsten und einer Entzundereinrichtung sowie einem Induktionsofen zwischen diesen und

Fig. 6

in der Darstellung nach Fig. 1 eine Gießwalzanlage in einer weiteren alternativen Ausführungsform der Erfindung.

Show it:

Fig. 1

FIG. 2 schematically shows a casting and rolling plant according to a first embodiment of the invention, FIG.

Fig. 2

in the illustration Fig. 1 a cast roll mill in an alternative embodiment of the invention,

Fig. 3

in the illustration Fig. 1 a cast roll mill in a further alternative embodiment of the invention,

Fig. 4

schematically the area between the caster and the rolling train with scissors and means for thermal insulation,

Fig. 5

schematically the section of the finishing mill with two rolling stands and a descaling and induction furnace between them and

Fig. 6

in the illustration Fig. 1 a cast roll plant in a further alternative embodiment of the invention.

In Fig. 1 is a cast roll plant to see in which a metal strip 1 is produced. For this purpose, a thin slab 3 is first cast in a known casting machine 2, which is then fed to a rolling train 4, 5, which in the present case consists of a roughing train 4 and a finishing train 5.

In order to enable both a continuous and a discontinuous operation in the sense of the above statements, both a holding furnace 6 and an induction furnace 7 are provided in front of the rolling train 4, 5. The operation of the two furnaces 6, 7 is carried out by a corresponding control (not shown) such that the correct strip temperatures are available for both operating modes. The necessary control or regulation processes are well known in the art.

The holding furnace 6 arranged behind the caster 2 may be a conventionally gas-fired furnace. The order of arrangement of holding furnace 6 and induction furnace 7 may be arbitrary.

According to the embodiment according to Fig. 1 The roughing train 4 has two rolling stands 10, while the finishing train 5 has five rolling stands 11. It can also be seen that a further induction furnace 8 is also arranged between the roughing train 4 and the finishing train 5 in order to heat the belt after rough rolling in the roughing train 4 to the optimum belt temperature before finish rolling in the finishing train 5. Furthermore, in the embodiment according to Fig. 1 also arranged between some rolling stands 11 of the finishing train 5 induction furnaces 9, to keep the band still optimally temperature-controlled.

Between the caster 2 and the holding furnace 6 a strip shear 13 is arranged. Furthermore, a band shears 14 is also positioned behind the finishing train 5. What is new is that in the conveying direction of the thin slab 3 and the metal strip 1 behind the first induction furnace 7 and in front of the finishing train 5, a further strip shear 12 is arranged.

The scissors 13 are used for separating the thin slabs 3 in the batch mode and the scissors 14 for separating the bands in endless rolling.

The scissors 12 is used to Schopfen the tape head or tape end when starting or Ausfördem in continuous operation or in discontinuous operation to ensure safe transport through the behind arranged active inductive heaters.

The system continues to be equipped with elements known per se. These include descaling devices 15, which are positioned at a favorable process site. Furthermore, behind the finishing train 5, a cooling line 16 is present. Similarly, reels 17 are arranged at the end of the system.

In Fig. 2 is a plant concept to see that provides a roughing 4 with three rolling stands 10 and a finishing train 5 with four rolling stands 11. Otherwise, the solution shown there corresponds to that according to Fig. 1 ,

Fig. 3 shows a system with a compact finishing line, ie here does not exist the roughing 4 in the sense of the solutions according to the FIGS. 1 and 2 , In the present case, the compact finishing train 5 has seven rolling stands 11, which finish the metal strip 1 after the induction furnace 7. Between the finishing stands further inductive heating units 9 are provided.

By using the proposed plant types, a coupled fully continuous casting-rolling process (continuous rolling) and optionally a decoupled discontinuous use of individual slabs (batch-rolling) is possible.

The furnace 6 - preferably designed as a roller hearth furnace - serves as a holding furnace during discontinuous operation and is advantageously carried out briefly, so that a thin slab 3 finds space in it. As a result, the cooling of the thin slab during transport is prevented with casting speed. With the inductive heating 7, the thin slab 3 is reheated during continuous operation (continuous operation) or discontinuous operation. In this case, the heat input depending on the casting speed can be set individually, so that when leaving the thin slab 3 from the inductive heating 7 results in a constant temperature at the desired level. Another advantage of the inductive heater 7 compared to a gas-fired furnace results from the short length with correspondingly high heat output.

In Fig. 4 is schematically seen the area between the casting machine 2 and the rolling mill or the holding furnace 6, which is provided with the scissors 13. Especially in continuous operation, where rolling is performed at the low casting speed, it is important to minimize the heat loss. For this purpose, in the embodiment between the casting machine 2 and the furnace 6 in the region of the scissors 13 (and in front of and behind the induction heating) of the roller table with thermal insulation means 18, 19 is provided. In the present case, these means are designed as thermal insulation panels, which are arranged between the rollers of the roller conveyor and above the roller table rollers. The heat-insulating means 18 are arranged stationary.

In the area in which movements take place (for example in the area of the scissors 13), it is not customary to arrange thermal insulation means, since a Schopfschnitt is carried out at regular time intervals. In continuous operation, however, the scissors are not active for a long time, so that it is provided in the embodiment, also to isolate the area of the scissors close to and below the slab 3 and the band 1, to positively influence the energy balance. Ie. the roller shutter cover is normally active, only when it is intended to make a cut (namely at the start of casting or during batch rolling), the heat-insulating means 19 are moved by means of movement means 20 (shown in FIG Fig. 4 only very schematically indicated by a double arrow) moved from the insulation area in a waiting position, in particular swung out.

With the described thermal insulation, a temperature loss can be prevented.

Since the rolling process takes place relatively slowly in the endless process, it makes sense to perform a descaling of the surface of the slab 3 or of the strip 1 between the front rolling stands and then to heat the strip. This has a positive effect on the surface quality. A device-technical design of this type is out Fig. 5 out. Here is the To see area between two rolling stands 11 of the finishing train 5, wherein in the conveying direction F of the belt 1 and the slab 3, a descaling device 15 is first arranged. A looper 22 and a hold-down roller 23 hold the band 1 on tension. The strip 1 then passes into an induction furnace 9 and then via a transfer table 24 and a side guide 25 to the following rolling stand 11. The order of the rolling stands, ovens and descaling can also be combined in any other way.

As explained above, it can be provided that a holding furnace and an induction furnace are arranged one behind the other, although the order can be arbitrary. In particular, the induction heating can also be arranged in front of the holding furnace.

Furthermore, it is possible, behind a first furnace in the form of a holding furnace 6 and an adjoining in the conveying direction F induction furnace 7 still a compensation furnace 21 to arrange, as it is Fig. 6 evident.

Especially in the generation of a particularly high temperature at the entrance of the finishing train, the z. B. komorientierten silicon steel may be necessary, this is an advantage. Here, the first furnace 6 is a heating furnace, which is supported by the induction furnace 7. For the purpose of homogenizing the temperature distribution over the bandwidth and thickness of the equalizing furnace 21 is advantageous. This furnace configuration is preferably for the illustrated process, but it can also be used in a conventional CSP plant, i. H. in batch mode.

In continuous rolling, the level of casting speed determines the temperature profile throughout the plant. Depending on the casting speed, a computational model dynamically controls the heating powers of the inductive heaters before and within the rolling mill such that the rolling mill run-off temperature reaches the target temperature.

If the casting speed falls below a certain predetermined threshold value (in the case of problems in the casting plant, in the case of difficult-to-cast materials, during the start-up process, etc.), automatic switching from endless mode to discontinuous rolling takes place.

That the thin slab 3 is separated with the scissors 13 and the rolling speed is increased so that the desired final rolling temperature is reached. The slab or belt segments within the road 4, 5 are tracked and adjusted dynamically depending on the temperature distribution, the transport or rolling speed and inductive heating across the belt length.

If the casting process has stabilized again and the casting speed exceeds the predetermined minimum value, then analogous to the discontinuous operation, it is switched back into the endless mode.

When endless rolling inductive heaters 9 are used within the finishing train 5 in the rule, the discontinuous operation or the startup process on the tape head they are in a secure waiting position far away above or next to the tape.

By any switching or setting of continuous operation or discontinuous operation is given a high degree of flexibility, which represents an increase in process reliability. This is especially true when commissioning a production plant.

The endless mode during processing will not be generally used; Batch operation will be used primarily for casting speed problems or during startup.

In order to optimize energy can be provided, mainly thinner or difficult to produce tapes in the endless mode and tapes with thicknesses greater than a critical thickness in batch operation at high speed and thereby low heat energy requirement to roll. The right combination of generation method optimizes the energy balance of the CSP continuous batch system for the entire product mix.

LIST OF REFERENCE NUMBERS

1

metal band

2

casting machine

3

thin slab

4, 5

rolling train

4

roughing

5

finishing line

6

Holding furnace (roller hearth furnace)

7

induction furnace

8th

induction furnace

9

induction furnace

10

Rolling mill of the roughing mill

11

Roll stand of the finishing train

12

tape cutter

13

tape cutter

14

tape cutter

15

descaling

16

cooling section

17

reel

18

heat insulator

19

heat insulator

20

means

21

soaking furnace

22

Looper

23

Down roller

24

transfer table

25

cornering

F

Belt conveying direction

Claims (26)

1. Method of producing a metal strip (1) by casting-rolling, in which initially a thin slab (3) is cast in a casting machine (2), wherein this is subsequently rolled in at least one rolling train (4, 5) with use of the primary heat of the casting process, wherein the cast thin slab (3) passes, between the casting machine (2) and the at least one rolling train (4, 5), not only at least one holding oven (6), but also at least one induction oven (7), characterised in that the holding oven (6) and the induction oven (7) are activated or deactivated or controlled or regulated in dependence on a selected mode of operation, namely a first mode of operation of continuous production of the metal strip (1) and a second mode of operation of discontinuous production of the metal strip (1).
2. Method according to claim 1, characterised in that the rolled metal strip (1) is also heated in strip conveying direction (F) behind a first rolling train (4) in at least one further induction oven (8, 9), wherein the at least one further induction oven (8, 9) is activated or deactivated or controlled or regulated in dependence on the selected operating mode.
3. Method according to claim 1 or 2, characterised in that the selection of the operating mode is carried out in dependence on the final thickness, which is to be produced, of the metal strip (1).
4. Method according to any one of claims 1 to 3, characterised in that the selection of the operating mode is carried out in dependence on the casting speed of the thin slab (3).
5. Method according to claim 1 or 2, characterised in that the selection of the operating mode is carried out in dependence on the product of thickness, which is to be produced, and speed of the metal strip (1) or of the thin slab (3).
6. Method according to any one of claims 1 to 5, characterised in that in the case of the selected operating mode of discontinuous production of the metal strip (1) the thin slab (3) is kept, charge-by-charge, in the holding oven (6) at a desired temperature before it is conveyed to the rolling train (4, 5).
7. Method according to any one of claims 1 to 5, characterised in that in the case of the selected mode of operation of continuous production of the metal strip (1) the thin slab (3) is brought in the holding oven (6) to a desired temperature and subsequently heated to the desired rolling temperature by means of the at least one induction oven (7, 8, 9) directly prior to the rolling process in the rolling train (4, 5).
8. Method according to claim 7, characterised in that the heat intake into the thin slab (3) is carried out by the at least one induction oven (7, 8, 9) in dependence on the casting speed as well as the exit temperature from the casting machine (2) or holding oven (6).
9. Method according to any one of claims 1 to 8, characterised in that the delivery of heat from the heating metal strip (1) or from the heated thin slab (3) to the environment is impeded by heat insulating means (18, 19).
10. Method according to claim 9, characterised in that at least a part of the heat insulating means (18, 19) is moved, in dependence on the desired mode of operation of the casting-rolling plant, into the region of the metal strip (1) or the thin slab (3) or out of this region.
11. Method according to any one of claims 1 to 10, characterised in that the metal strip (1) or the thin slab (3) is descaled in the rolling train (4, 5) in a region, which is at the front in strip conveying direction (F), of the rolling train (4, 5) and subsequently thereto heated in a region adjoining in strip conveying direction (F).
12. Method according to claim 11, characterised in that the descaling of the metal strip (1) or of the thin slab (3) is carried out by means of a descaling device (15) and the heating of the metal strip (1) or of the thin slab (3) is carried out by means of an induction oven (8, 9) between two roll stands (10, 11).
13. Method according to claim 12, characterised in that the heating follows the descaling in strip conveying direction (F).
14. Method according to claim 12, characterised in that the descaling follows the heating in strip conveying direction (F).
15. Device for producing a metal strip (1) by casting-rolling, with a casting machine (2), in which initially a thin slab (3) is cast, and at least one rolling train (4, 5), which is downstream of the casting machine (2), in which the thin slab (3) is rolled with use of the primary heat of the casting process, particularly for carrying out the method according to any one of claims 1 to 14, wherein arranged between the casting machine (2) and the at least one rolling train (4, 5) are at least one holding oven (6) and at least one induction oven (7), characterised in that control means are present by which the holding oven (6) and/or the induction oven (7) is or are activated or deactivated or controlled or regulated in dependence on a selected mode of operation, namely a first mode of operation of continuous production of the metal strip (1) and a second mode of operation of discontinuous production of the metal strip (1).
16. Device according to claim 15, characterised in that initially a holding oven (6) and then an induction oven (7) are arranged in conveying direction (F) of the thin slab (3) or the metal strip (1).
17. Device according to claim 15, characterised in that initially an induction oven (7) and then a holding oven (6) are arranged in conveying direction (F) of the thin slab (3) or the metal strip (1).
18. Device according to any one of claims 15 to 17, characterised in that a blooming train (4) and a finishing train (5) are provided, wherein at least one further induction oven (8) is arranged between the blooming train (4) and the finishing train (5).
19. Device according to any one of claim 15 to 18, characterised in that at least one further induction oven (9) is arranged between two roll stands (10, 11) of the blooming train (4) and/or of the finishing train (5).
20. Device according to any one of claims 15 to 19, characterised in that a strip cutter (12) is arranged behind the induction oven (7), which is first in conveying direction of the thin slab (3) or of the metal strip (1), and ahead of the finishing train (5).
21. Device according to any one of claims 15 to 20, characterised in that a strip cutter (13), which is used primarily in a discontinuous rolling process, is arranged behind the casting machine (2) in the conveying direction of the thin slab (3) or of the metal strip (1) and ahead of the holding oven (6).
22. Device according to any one of claims 15 to 21, characterised in that a strip cutter (14), which is used for parting the metal strips in the continuous mode, is arranged behind the finishing train (5) in conveying direction of the thin slab (3) or of the metal strip (1).
23. Device according to any one of claims 15 to 22, characterised in that heat insulating means (18, 19) for impeding the delivery of heat from the heated metal strip (1) or from the thin slab (3) to the environment are provided and are arranged at least partly in the region of the metal strip (1).
24. Device according to claim 23, characterised in that movement means (20) are present, by which at least a part of the heat insulating means (18, 19) can be moved into the region of the metal strip (1) or the thin slab (3) or out of this region.
25. Device according to any one of claims 15 to 24, characterised in that at least one descaling device (15) is present, which is arranged in a region of the rolling train (4, 5) at the front in strip conveying direction (F).
26. Device according to any one of claims 15 to 25, characterised in that a holding oven (6), an induction oven (7) and a compensating oven (21) are arranged in this sequence in front of the rolling train (4, 5) in conveying direction (F) of the thin slab (3) or the metal strip (1).

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